Abstract: 【Objective】 The aim of the current study is to reveal the evolutionary relationships, and investigate the protein structure and functions and the expression profiles of calreticulin (CRT) as a key Ca²⁺ binding molecular chaperone within the endoplasmic reticulum (ER) of chicken.【Method】The nucleotides and amino acids of CRT in 12 species of vertebrates recorded in Gene bank were analyzed for evolutionary relationships by Laser Gene, and the structures and functions of CRT protein in chicken were predicted by bioinformatics, and the expression profiles of CRT in 30 organizations of chicken was analyzed by real-time PCR.【Result】Results of homology analysis showed that compared with the other 11 species of nucleotide sequences of CRT gene in chicken, gallus gallus and oryctolagus cuniculus had the highest nucleotide sequence homology, which was 78.7%, in addition, gallus gallus and oncorhynchus mykiss had the lowest homology, which was 70.5%. In the homology of amino acid sequences, the relationship between gallus gallus and crotalus adamanteus cadam is the closest by 85.0%, and the furthest relationships with gallus gallus is oncorhynchus mykiss which was 69.0% in amino acid sequence, besides, the homology of gallus gallus with cricetulus griseus, macaca mulatta, homo sapiens, oryctolagus cuniculus, sus scrofa, bos taurus, and xenopus (silurana) tropicalisis relatively close to almost above 80.1%. The protein structure and function prediction revealed that the CRT of chicken was constitute with 404 amino acids, and had a relative molecular mass of 46.8802 kD and a theoretical isoelectric point of 4.41, moreover, the negative charge is 102 amino acid residues and the positive charge amino acid residues is 53. The molecular formula of the CRT was C₂₀₇₄H₃₁₀₇N₅₄₃O₆₈₄S₉. The CRT of chicken had 22 hydrophobic regions, which of the C end and the N end had a high hydrophobic, while the hydrophilic of C end is stronger than that of N, and the protein formed a secondary structure as α_1(7-17)-α_2(22-25)-β₁₍₂₆₎- β_2(38-41)-β_3(50-54)-β_4(69-70)-β_5(75-82)-β_6(92-99)-β_7(110-114)-β_8(129-133)-β_9(144-151)-β_10(171-178)-β_11(183-187)-β_12(314-322)-β_13(326-332)-α_3(337-348)-α_4(350-375)- α_5(377-379)-α_{6(395- 401)}. CRT belongs to the transmembrane proteins and secreted protein, has signal peptides. The enzyme classification of CRT was EC 3.2.1.55 or EC 3.4.24.68. Tissue expression assay indicated that the gene of CRT expressed widely in chicken tissues, in which the lleum, glandular stomach and duodenum were highly more than the kidney (control) by 20 times. 【Conclusion】The sequence of nucleotide and amino acid in chicken CRT is relatively conserved in 12 vertebrate species. CRT is a transmembrane secretion protein and acidic protein. It belongs to the alpha-N-Arabia-glucosidase or Tentoxilysin, which catalyzed the hydrolysis  of the end non-reducing α-L-arabinofuranosidase residues in the terminal of α-L-arabinoside, which effected the α-L- arabinofuranosidase, Arabic glycans containing (1,3) and/or (1,5) glucosidic bond, Arab xylan and arabinogalactan. CRT combined specifically with the carbohydrate molecules and Ca²⁺, which could monitor glycoprotein assembly and folding and Ca²⁺ regulation, and plays an important role in the digestive system.

Key words: chicken, Calreticulin, structure and functions, expression profiles, evolutionary relationship